Reconfigurable Clamping System

ABSTRACT

A clamping system can be reconfigured to clamp any of multiple workpieces having differing shapes. The system includes a retention assembly for retaining an inflatable bladder that applies a clamping force to the workpiece. The retention assembly includes a flexible chain of pivotally connected links that can be locked in place to form a rigid assembly that conforms to the shape of the workpiece. The links can be unlocked to allow reconfiguration of the retention assembly into shapes matching other workpieces.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional U.S. PatentApplication No. 60/849,688 filed Oct. 5, 2006.

TECHNICAL FIELD

This disclosure generally relates to systems for clamping workpieces,and deals more particularly with a clamping system that can bereconfigured to match the contours of workpieces having differingshapes.

BACKGROUND

Various types of known clamping systems may be used to hold workpiecesduring manufacturing operations such as machining, routing, cutting andwelding. These systems may include combinations of toe-clamps, springclamps, hold-down bars, constant mold-line bladder tools and set screwsthat are configured to clamp the workpiece to a base. For example, onesuch clamping system is disclosed in US Patent Application PublicationNo. US 2006/0237888 A1 owned by The Boeing Company in which aninflatable bladder is held against a workpiece by a rigid retaining barfastened to a base. Inflation of the bladder applies a clamping force tothe workpiece.

While clamping systems of the type described above provide satisfactoryresults, they may be limited in their use to workpieces having aparticular configuration or surface contour. These clamping systems areoften custom-made to match the configuration of the particular workpieceto be clamped, and thus may not be readily adaptable to clamp workpieceshaving other configurations.

Accordingly, there is a need for an adaptable clamping system that maybe readily reconfigured for clamping workpieces having a variety ofconfigurations, thereby avoiding the cost of fabricating clampingelements that are unique to a particular workpiece configuration.Illustrated embodiments of the disclosure are intended to satisfy thisneed.

SUMMARY

The disclosed embodiments provide a reconfigurable clamping system inwhich a flexible retention assembly can be reconfigured for use with anyof multiple workpieces having differing feature configurations, or asingle workpiece having varying surface contours. The retention assemblymay be reconfigured easily and quickly without the need for specialtools or clamping elements that are unique to a particular workpiececonfiguration.

According to one embodiment of the disclosure, a clamping system isprovided for securing a workpiece comprising: a retention assembly thatmay be positioned over the workpiece, including a plurality of links; apivotal connection between each of the links allowing the retentionassembly to be configured to the general shape of the workpiece; and, aninflatable bladder positioned between the retention assembly and theworkpiece for applying a clamping force to the workpiece. The links maybe Z-shaped and arranged in overlapping, nested relationship with eachother. A locking mechanism is, provided for locking the configuration ofthe retention assembly to match the configuration of a particularworkpiece. The locking mechanism may include spline gears on opposingfaces of adjacent links, and fasteners which clench the gears togetherto lock the links in a desired configuration. A spring may be usedbetween the links for biasing the opposing spline gears away from eachother, to allow free rotation of the links during a reconfigurationprocess. A recess may be provided in the bottom of the links which formsa channel for holding the bladder assembly.

According to another disclosed embodiment, a reconfigurable clampingsystem is provided for securing a workpiece, comprising: a retentionassembly reconfigurable to generally match the shape of differingworkpieces; a locking device for locking the retention assembly in adesired configuration generally matching the shape of a workpiece; and,an inflatable bladder positioned between the retention assembly and theworkpiece for applying a clamping force to the workpiece. The retentionassembly may include a chain of pivotally connected links, and lockingelements for locking the links against pivotal movement relative to eachother. The locking device may include interlocking elements respectivelyon opposing faces of the links for locking the links against pivotalmovement in order to fix the configuration of the retention assembly tomatch the configuration of a particular workpiece.

According to a method embodiment of the disclosure, clamping a workpieceduring a manufacturing operation comprises the steps of: configuring aflexible retention assembly to generally match the shape of theworkpiece; fixing the configuration of retention assembly to form arigid retention assembly; bridging at least a portion of the workpiecewith the rigid retention assembly; placing a bladder between the rigidretention assembly and the workpiece; and, inflating the bladder. Theretention assembly is configured by placing a flexible chain of linksover the workpiece to generally conform to the workpiece. Theconfiguration of the retention assembly may be fixed by locking theposition of the links relative to each other. The method may includereconfiguring the retention assembly to match the shape of multipleworkpieces having differing contours or feature configurations.

Other features, benefits and advantages of the disclosed embodimentswill become apparent from the following description of embodiments, whenviewed in accordance with the attached drawings and appended claims.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1 is an exploded, isometric illustration of a workpiece and asubstructure on which the workpiece is to be clamped.

FIG. 1A is a functional block diagram illustrating a clamping system forclamping the workpiece on the substructure.

FIG. 2 is a view similar to FIG. 1 but showing the workpiece clamped onthe support structure using the clamping system according to anembodiment of the disclosure.

FIG. 3 is an enlarged, perspective illustration of the reconfigurableclamping system shown in FIG. 2.

FIG. 4 is a cross sectional illustration of the clamping system, shownin relation to the workpiece and a tool.

FIG. 5 is a sectional illustration showing details of the clampingsystem.

FIG. 6 is a side illustration of a portion of one of the links, betterdepicting a spline gear.

FIG. 7 illustrates the bottom of one of the links, better showing arecess channel for retaining an inflatable bladder.

FIG. 8 is a block diagram illustration of a method for clamping aworkpiece according to a method embodiment of the disclosure.

FIG. 9 is a flow diagram of an aircraft production and service method.

FIG. 10 is a block diagram of an aircraft.

DETAILED DESCRIPTION

Referring to FIGS. 1-7, the disclosed embodiments relate to a clampingsystem generally indicated at 20 for clamping a workpiece 10 on asubstructure 12. As shown in FIG. 1A, the clamping assembly 20 broadlycomprises a retention assembly 22 and an inflatable bladder 30 forapplying a clamping force 17 the workpiece 10. The retention assembly 22includes a plurality of links 22 coupled together by pivotal connections19. The retention assembly 22 retains the inflatable bladder 30 inposition over the workpiece 10. Inflation of the inflatable bladder 30results in the application of the clamping force 17 to the workpiece 10.The substructure 12 applies a reactive force 21 to the workpiece 10,causing the workpiece 10 to be clamped between the substructure 12 andthe clamping assembly 20.

In the illustrated embodiment, the workpiece 10 comprises a skin that isintended to be fastened, as by welding, to a substructure 12 that mayform, for example, part of an aircraft. A series of spaced mounting postassemblies 16 are positioned on opposite sides of the substructure 12and each include a mounting plate 18. The mounting plates 18 have acommon hole pattern allowing any of identical clamping assemblies 20 tobe secured to the mounting post assemblies 16 using mounting blocks 23and hold down fasteners 24. An adjustment screw such as a set screw 25may be used to adjust the attitude of the mounting blocks 23 on theplates 18. Mounting post assemblies 16 along with the substructure 12are supported on a common base 14.

In the illustrated example, the workpiece 10 has a cross section that isgenerally bell shaped which changes in contour from the front to therear, as viewed in FIGS. 1 and 2. For sake of simplicity, only a singleclamping system 20 is shown in FIG. 2, however in practice it should beunderstood that a plurality of the clamping systems 20 may be employedto clamp the workpiece 10 to the substructure 12 along its length. Inthe embodiment illustrated in FIGS. 1 and 2, four clamping systems 20may be used which bridge the width of the workpiece 10 and arerespectively supported on the mounting post assemblies 16.

The clamping system 20 may be employed to hold down a workpiece 10during any of a variety of manufacturing operations such as machining,routing, cutting or welding. In the illustrated example, a tool 26 inthe form of a friction stir welding (FSW) head is used to weld the skin10 to the substructure 12. As will be discussed later in more detail,the clamping system 20 may be readily reconfigured to clamp workpieces10 having part features, configurations or surface contours other thanthose illustrated in the drawings. Moreover, a plurality of identicalclamping systems 20 may be employed to hold down various areas of aparticular workpiece 10 even though the surface contour of the workpiece10 may vary over its surface.

The retention assembly 22 is pivotally connected to the mounting blocks23. The inflatable bladder 30 functions as a hold-down intensifier thatholds and pushes the workpiece against the substructure 14. When lockedin a rigid, clamping position as described later herein, the retentionassembly 22 generally conforms to the shape of the workpiece 10 andfunctions to retain the inflatable bladder 30 while the inflatablebladder 30 is inflated to apply clamping force to the workpiece 10. Theends of the retention assembly 22 are secured to the mounting plates 18by the mounting blocks 23 and hold down fasteners 24.

The retention assembly 22 includes a chain of Z-shaped, pivotallyconnected links 28 arranged on overlapping, nested relationship. Eachend of each of the links 28 includes a through-hole 48 (see FIGS. 5-7)for receiving a fastener which may comprise a bolt 34 having a threadedend for receiving a nut 36. The bolt 34 forms a pivotal connectionbetween adjacent ones of the links 28. Washers 38 may be provided tobetter distribute clamping forces to the links 28. One end of each ofthe links 28 may include a counterbore recess 42 in order to recess thenut 36. A spring 40, which may be a Bellville washer or a spring washerfor example, is sleeved over the bolt 34 and positioned between opposingfaces 29 (FIGS. 5 and 6) in order to normally bias the faces 29 awayfrom each other.

The opposing faces 29 of the links 28 each include interlocking elementswhich may comprise circular spline gears 32 circumferentially arrangedaround the through-hole 48. The spline gears 32 may be formed in theopposing faces 29 of the links 28 by machining, molding or other commonfabrication techniques. The spline gears 32 provide radial features 50which meshingly engage the corresponding features 50 on an opposing face29 when the links are clenched together, so as to interlock the links 28in a desired rotational position, allowing the links 28 to conform tothe shape of the workpiece 10.

As best seen in FIGS. 4, 5 and 7, each of the links 28 includes a recess46 on the bottom side thereof facing the workpiece 10. The recesses 46in the links 28 collectively form a channel 52 that has a width “W”(FIG. 7) and extends substantially the entire length of the retentionassembly 22. The inflatable bladder 30 is retained within the channel 52and may include a flat rib 44 on the upper side thereof which engagesthe bottom of the links 28 and thereby better distributes force betweenthe retention assembly 22 and the workpiece 10.

In one particular embodiment, the inflatable bladder 30 may comprise asilicon hose including NOMEX fiber manufactured by Presray Pneuma-sealof Pawling Engineered Products. The inflatable bladder 30 with NOMEXfiber retains approximately 80% of its strength at 400° F., permittinghigh temperature manufacturing operations to be undertaken on theworkpiece 10 in close proximity to the retention assembly 22. By way ofexample, but not limitation, in friction stir welding applications ofapproximately ⅛″ aluminum skin to an underlying substructure, theinflatable bladder 30 is suitably inflated to about between 10 and 80psi. The friction stir welding tool 26 may then engage the workpiece 10in the area immediately around the retention assembly 22 while theinflatable bladder 30 maintains clamping pressure on the workpiece 10,despite the heat generated by the welding tool 26.

Referring now to FIG. 8, a method of clamping a workpiece begins at step54 in which the retention assembly 22 is bridged over the workpiece 10so that the ends of the retention assembly 22 lie generally over themounting plates 18. At this stage, the links 28 freely pivot relative toeach other as a result of the outward biasing force imposed by thesprings 40 which force the spline gears 32 apart so that they areunlocked. Therefore, the retention assembly 22 is freely flexible andthus may conform to the surface configuration and contours of theworkpiece 10. The retention assembly 22 is configured at step 56 bymanually manipulating the links 28 to conform to the surface contours ofthe workpiece 20.

Next, at step 58, the links 28 are locked in place by tightening thenuts 36. Tightening of the nuts 36 draws adjacent links 28 together,bringing the opposing spline gears 32 into interlocking engagement whichlocks the links 28 against pivotal movement. Tightening of the nut 36effectively clenches the spline gears 32 together, against the biasinginfluence of the spring 40. After tightening each of the nuts 36 for allof the links 28, the retention assembly 22 becomes a rigid assemblyhaving a shape generally matching that of the contour or configurationof the workpiece 10 in the area where the clamping assembly 20 has beeninstalled.

With the retention assembly 22 having been configured, the inflatablebladder 30 is then installed within the channel 52, between theretention assembly 22 and the workpiece 10, as shown at step 60. Next,at step 62, the retention assembly 22 is secured to the mounting postassemblies 16 by fastening the mounting blocks 23 to the plates 18 usingthe hold down fasteners 24. The inflatable bladder 30 is then inflatedat step 64, resulting in a clamping force being applied to the workpiece10 as the retention assembly 22 holds and retains the inflatable bladder30. The retainer assembly 22 resists the load imposed by the inflatablebladder 30, causing the inflatable bladder 30 to hold the workpiece 10to the substructure 12. The inflatable bladder 30 also makes up the gapbetween the retention assembly 22 and the workpiece 10 so that theretention assembly 22 tightly conforms to the contour of the workpiece10.

With the workpiece 10 securely clamped, any of various operations suchas friction stir welding may be performed on the workpiece 10, as shownin step 66. When the operations on the workpiece 10 are complete, theinflatable bladder 30 is deflated at step 68 following which theretention assembly 22 is released from the base 14, as shown in step 70,by unfastening the mounting blocks 23 from the mounting plates 18. Next,at step 72, the links 28 are unlocked so that the retention assembly 22may be later configured to hold a different workpiece 10. This unlockingprocess comprises loosening (unscrewing the nuts 36 until the springs 40to force the opposing faces 29 apart, thereby unlocking the spline gears32. At this point, the retention assembly 22 is again freely flexible,allowing it to be reconfigured to match the contour of a new workpiece,as shown at step 74.

The embodiments of the disclosure described above may be used in anaircraft manufacturing and service method 76 as shown in FIG. 9 and anaircraft 106 as shown in FIG. 10. During pre-production, exemplarymethod 100 may include specification and design 78 of the aircraft 106and material procurement 80 During production, component and subassemblymanufacturing 82 and system integration 84 of the aircraft 106 takesplace. Thereafter, the aircraft 106 may go through certification anddelivery 86 in order to be placed in service 88. While in service by acustomer, the aircraft 106 is scheduled for routine maintenance andservice 90 (which may include modification, reconfiguration,refurbishment, and so on).

Each of the processes of method 76 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer),as indicated by the “X” in the grid to the right of the flow diagram ofFIG. 9. For the purposes of this description, a system integrator mayinclude without limitation any number of aircraft manufacturers andmajor-system subcontractors; a third party may include withoutlimitation any number of venders, subcontractors, and suppliers; and anoperator may be an airline, leasing company, military entity, serviceorganization, and so on.

As shown in FIG. 10, the aircraft 106 produced by exemplary method 76may include an airframe 92 with a plurality of systems 94 and aninterior 96. Examples of high-level systems 94 include one or more of apropulsion system 98, an electrical system 100, a hydraulic system 102,and an environmental system 104.

Apparatus and methods embodied herein may be employed during any one ormore of the stages of the production and service method 76. For example,components or subassemblies corresponding to production process 82 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while the aircraft 106 is in service. Also, oneor more apparatus embodiments, method embodiments, or a combinationthereof may be utilized during the production stages 82 and 84, forexample, by substantially expediting assembly of or reducing the cost ofan aircraft 106. Similarly, one or more of apparatus embodiments, methodembodiments, or a combination thereof may be utilized while the aircraft106 is in service, for example and without limitation, to maintenanceand service 90.

Although the embodiments of this disclosure have been described withrespect to certain exemplary embodiments, it is to be understood thatthe specific embodiments are for purposes of illustration and notlimitation, as other variations will occur to those of skill in the art.

1. A clamping system for securing a workpiece, comprising: a retentionassembly that may be positioned over the workpiece, the retentionassembly including a plurality of links; a pivotal connection betweeneach of the links allowing the retention assembly to be configured tothe general shape of the workpiece; and an inflatable bladder positionedbetween the retention assembly and the workpiece for applying a clampingforce to the workpiece.
 2. The clamping system of claim 1, wherein: eachof the links is Z-shaped, and the links are arranged in overlapping,nested relationship.
 3. The clamping system of claim 1, furthercomprising a locking mechanism for locking the configuration of theretention assembly.
 4. The clamping system of claim 3, wherein: thelinks include overlapping, opposing faces, and the locking mechanismincludes interlocking spline gears on the opposing faces of the links.5. The clamping system of claim 4, wherein the locking mechanismincludes means for clenching the spline gears together.
 6. The clampingsystem of claim 4, wherein the locking mechanism includes a threadedfastener for drawing the opposing faces together.
 7. The clamping systemof claim 4, wherein the locking mechanism includes a spring for normallybiasing the opposing faces away from each other.
 8. The clamping systemof claim 1, wherein: the retaining assembly includes a longitudinalchannel therein, and the bladder is retained within the channel.
 9. Theclamping system of claim 1, wherein the channel is defined by recessedareas in the bottom of each of the links.
 10. A reconfigurable clampingsystem for securing a workpiece, comprising: a retention assemblyreconfigurable to generally match the shape of differing workpieces; alocking device for locking the retention assembly in a desiredconfiguration generally matching the shape of a workpiece; and aninflatable bladder positioned between the retention assembly and theworkpiece for applying a clamping force to the workpiece.
 11. Theclamping system of claim 10, wherein the retention assembly includes achain of pivotally connected links.
 12. The clamping system of claim 11,wherein the locking device includes a plurality of Locking elements forlocking the links against pivotal movement relative to each other. 13.The clamping system of claim 11, wherein: adjacent ones of the linksoverlap and include opposing faces, and the locking device includesinterlocking elements respectively in the opposing faces for locking theadjacent links against relative pivotal movement.
 14. The clampingsystem of claim 11, wherein the links include a channel therein for atleast partially containing the bladder.
 15. The clamping system of claim11, wherein: each of the links includes a bottom face, and the bladderincludes a generally flat wall bearing against the bottom face of eachof the links.
 16. The clamping system of claim 11, wherein: each of thelinks includes a generally Z-shaped body, and the Z-shaped bodies arearranged in overlapping, nested relationship to each other.
 17. A methodfor clamping a workpiece during a manufacturing operation, comprisingthe steps of: (A) configuring a flexible retention assembly to generallymatch the shape of the workpiece; (B) fixing the configuration of theretention assembly configured in step (A) to form a rigid retentionassembly; (C) bridging at least a portion of the workpiece with therigid retention assembly; (D) placing a bladder between the rigidretention assembly and the workpiece; and, (E) inflating the bladder.18. The method of claim 16, wherein: step (A) includes placing aflexible chain of links over the workpiece to generally conform to theworkpiece, and step (B) includes fixing the positions of the linksrelative to each other.
 19. The method of claim 18, wherein fixing thepositions of the links includes clenching adjacent ones of the links inthe chain to prevent relative movement between the links.
 20. The methodof claim 17, further comprising the step of: (F) securing the ends ofthe rigid retention assembly to a base.
 21. The method of claim 17,further comprising the step of: (G) specifying and designing theworkpiece.
 22. The method of claim 17, further comprising the step of:(G) procuring the material used to manufacture the workpiece.
 23. Themethod of claim 17, wherein clamping the workpiece forms part of anoperation for manufacturing an aircraft subassembly.
 24. A method forclamping each of at least first and second differently shapedworkpieces, comprising the steps of: (A) configuring a flexibleretention assembly to a first shape at least generally matching theshape of the first workpiece; (B) locking the flexible retentionassembly configured in step (A) to form a rigid retention assemblyhaving the first shape; (C) bridging at least a portion of the firstworkpiece with the rigid retention assembly having the first shape; (D)placing a bladder between the rigid retention having the first shape andthe workpiece; (E) inflating the bladder; (F) unlocking the rigidretention assembly having the first shape; (G) reconfiguring theflexible retention assembly to a second shape at least generallymatching the shape of the second workpiece; (H) locking the flexibleretention assembly reconfigured in step (G) to form a rigid retentionassembly having the second shape; (I) bridging at least a portion of thesecond workpiece with the rigid retention assembly having the secondshape; (J) placing a bladder between the rigid retention assembly havingthe second shape and the workpiece; and (K) reinflating the bladder. 25.The method of claim 24, wherein: step (A) includes placing a flexiblechain of links over the first workpiece to generally conform to thefirst workpiece, and step (B) includes fixing the positions of the linksrelative to each other.
 26. The method of claim 25, wherein fixing thepositions of the links includes clenching adjacent ones of the links inthe chain to prevent relative movement between the links.